The Ministry of Defence confirmed today that it has suffered virus infections which have shut down "a small number" of MoD systems, most notably including admin networks aboard Royal Navy warships.

The Navy computers infected are the NavyStar (N*) system, based on a server cabinet and cable-networked PCs on each warship and used for purposes such as storekeeping, email and similar support functions. N* ship nets connect to wider networks by shore connection when vessels are in harbour and using satcomms when at sea.

The system is supplied by Fujitsu, with most of the Navy's fleet being equipped in the early years of the century. N* is intended to stay in service, coming under the Defence Information Infrastructure now being rolled out.

N* hardware varies in detail depending on when a ship had the system installed and when it has last had dockyard maintenance, but is based on industry-standard PCs with ruggedised cases and shock mounting (to cope with combat damage) and strict emissions certification to avoid interference with other systems.

Various MoD computers and N* nets aboard warships including the carrier Ark Royal have suffered N* outages over the past fortnight, caused by virus infection. A major impact has been the loss of email service, which in recent years has come to be a routine way for sailors to stay in touch with friends and family.

An MoD spokesperson supplied the Reg with a statement this afternoon:

Since 6 Jan 09 the performance of the MOD IT systems in a number of areas was affected by a virus. Immediate action was taken to isolate the problem to stop the virus from spreading. This meant that some people were without regular IT access (i.e. email, internet). There have been no infections detected on any networks with sensitive information.

A solution to prevent re-infection has been tested and implemented. The majority of systems are working normally. This is an ongoing process which we are working urgently on so for those people who are still off line normal business will resume as quickly as possible.

The MoD insisted that no command or operational systems had been affected, though many of these are based on similar hardware. Spokespersons also stated that "no classified or personal data has been or will be at risk of compromise" due to "pre-existing security measures".

The MoD refused to discuss details of the virus, transmission methods, countermeasures or other specifics of the incident "for security reasons".